An Investigation of the Initiation of Hollow Cathode Discharges
Abstract
Extensive investigations of the starting characteristics of several hollow cathode designs have revealed that this is a random process, dependent on temperature, mercury vapour flow rate, voltage, geometry, and the availability of a low work function material. For a given cathode and fixed conditions, the voltage necessary to start a discharge falls at random within a certain range. As temperature or flow rate are increased, the maximum value and width of this voltage range both decrease until, at high values, starting is reproducible at potentials often below 20V. This behavior appears to be strongly influenced by the site and rate of dispensation of the low work function material. A qualitative explanation of the results at high flow rate is proposed in terms of collisional ionisation of the vapour by thermionically emitted electrons. At lower flow rates, it is necessary to include electron reflection from the keeper electrode and perhaps, at the lowest flows, a vacuum arc mechanisms. Success was achieved in initiating discharges using internal electrodes, employing either low positive voltages or much higher negative potentials. In the former case, it was difficult to transfer the internal discharge through the cathode orifice to the keeper. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1976
- Accession Number
- ADA036079
Entities
People
- Angela S. Cox
- D. G. Fearn
- D. R. Moffitt
Organizations
- Royal Aircraft Establishment